Cathode ray tubes (CRTs) are frequently used in conjunction with a projection lens to provide an image. In normal use however, CRTs generate an amount of heat which is sufficient to undesirably degrade picture quality. In order to dissipate this heat, many CRTs utilize a cooling system having a liquid coolant which serves as a heat sink. In addition, the liquid coolant may be clear and colorless so as to serve as a liquid lens. Referring to FIG. 1, a CRT 10 and projection lens 12 are shown positioned within a chassis 14. The chassis 14 includes partitions 16 which together with a back surface 18 of the projection lens 12 form a chamber 20 for holding a liquid coolant 22 for dissipating heat. Referring to FIG. 2, an enlarged portion of the chassis 14 is shown. The chassis 14 further includes a fill hole 24 which is in fluid communication with the chamber 20. In use, the liquid coolant 22 is introduced into the fill hole 24 in order to fill the chamber 20. A fastener 26 is then inserted into the fill hole 24. The fastener 26 includes fastener threads 30 which are threaded with fill hole threads 32 to secure the fastener 26. The fastener 26 includes a sealing element such as an o-ring 28 which is compressed between the fastener 26 and a shoulder portion of the chassis 14 upon securing of the fastener 26 in the fill hole 24. This forms a seal which serves to maintain the liquid coolant 22 within the chamber 20.
However, such sealing arrangements have disadvantages. A disadvantage is that paint which may be present on the fastener threads 30 (due to paint overspray, etc.) may be removed due to contact with the fill hole threads 32. This generates paint particulates which ultimately contaminate the liquid coolant 22 and thus degrade picture quality. In addition, the liquid coolant 22 may be further contaminated by metal particulates which are generated due to metal to metal contact between the fastener 30 and fill hole 32 threads. Moreover, still further particulates may be generated due to cross threading of the fastener 30 and fill hole 32 threads, thus resulting in broken thread fragments which also contaminate the liquid coolant 22 and thus also degrade picture quality.
Another sealing arrangement is described in Japanese Utility Model No. 7-11399. This document discloses a CRT apparatus having a flexible, tube shaped sealing element which is positioned within a fill port used for introducing a liquid coolant. A shaft portion of an elongated fastener is positioned through the tube. A washer is located between an end of the tube and the head of the fastener. In use, the fastener is threaded into a portion of the chassis, thus urging the washer against the tube to compress the tube axially and expand the tube radially against inner portions of the fill port to form a seal. However, fabrication of the threads and assembly of the components is relatively time consuming and thus costly.